The research at the Laboratory for Comparative Biochemistry, supported by Grant HL-6950, continues on various aspects of the metabolism of red cells of man and different animals. A collaboration of many years with Dr. H. D. Kim of the University of Arizona emphasized during the current period studies of metabolic and membrane transport properties of pig reticulocytes. Our studies on pig, rat and rabbit reticulocytes are continuing and will be extended sonn to earlier stages in the maturation of the red cell. Research is also continuing to find out if the iron nucleotides, which we have discovered to be present in red cells, play some role in their metabolism and function. More work has been done in the past year and will be continuing on the identification and quantitation of red cell metabolites of fish, turtles and frogs at different stages of their development.